Characterization of an Environmentally Responsive Organic-Inorganic Hybrid Fe3O4/SiO2/PPy-c Core-Shell Nanocomposite with Magneto-Chromatic Ability for Synergistic Electrical Properties.

The aim of this study was to analyze the properties of a composite that incorporates carbon black and polypyrrole within an Fe3O4/SiO2 core-shell structure, synthesized using the Stöber method under high ultrasonic irradiation conditions (120 W) for Fe3O4/SiO2 nanocomposite. The Fe3O4/SiO2 core-shell indicates magnetochromatic behavior characterized by temperature-dependent coloration and magnetic alignment. Incorporating carbon black and polypyrrole at moderate temperature (5-15 °C) enhanced the electrical conductivity. The electrical resistivity ρ was 7.30 × 106 Ω·cm for Fe3O4, 3.19 × 108 Ω·cm for Fe3O4/SiO2, and 242.56 Ω·cm for Fe3O4/SiO2/PPy-c at room temperature. When it was performed at moderate temperature (5-15 °C), the ρ of the prepared Fe3O4/SiO2 and Fe3O4/SiO2/PPy-c nanocomposite was 1.08 × 108 and 0.00799 Ω·cm, respectively. Current-voltage measurements revealed a linear relationship, with butterfly shaped curves in the forward-bias region for all samples. The Fe3O4/SiO2/PPy-c nanocomposite's tunable synergistic electrical properties at moderate temperatures make it useful for environmental applications, electrical wiring, and circuitry.

One-Pot Synthesis of Tannic Acid-Au Nanoparticles for the Colorimetric Determination of Hydrogen Peroxide and Glucose.

This study introduces a novel one-pot method employing tannic acid (TA) to synthesize stable gold nanoparticles (TA-AuNPs), which are characterized using transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. We apply these TA-AuNPs in a newly developed colorimetric assay for hydrogen peroxide (H2O2) detection that utilizes the oxidation of iodide (I-) on TA-AuNPs, leading to a detectable yellow color change in the solution. The reaction kinetics are captured by the rate equation R = 0.217[KI]0.61[H2O2]0.69. The possible sensing mechanism was proposed through density functional theory calculations. At the optimum conditions, the proposed TA-AuNPs/I- system demonstrated a linear relationship between H2O2 concentration and absorbance intensity (λ = 350 nm) and achieved a limit of detection (LOD) of 7.33 µM. Furthermore, we expand the utility of this approach to glucose detection by integrating glucose oxidase into the system, resulting in a LOD of 10.0 µM. Application of this method to actual urine samples yielded spiked recovery rates ranging from 96.6-102.0% and relative standard deviations between 3.00-8.34%, underscoring its efficacy and potential for real-world bioanalytical challenges.

Combined Electrochemical Deposition and Photo-Reduction to Fabricate SERS-Active Silver Substrates: Characterization and Application for Malachite Green Detection in Aquaculture Water.

This research introduces a novel approach using silver (Ag) nanostructures generated through electrochemical deposition and photo-reduction of Ag on fluorine-doped tin oxide glass substrates (denoted as X-Ag-AgyFTO, where 'X' and 'y' represent the type of light source and number of deposited cycles, respectively) for surface-enhanced Raman spectroscopy (SERS). This study used malachite green (MG) as a Raman probe to evaluate the enhancement factors (EFs) in SERS-active substrates under varied fabrication conditions. For the substrates produced via electrochemical deposition, we determined a Raman EF of 6.15 × 104 for the Ag2FTO substrate. In photo-reduction, the impact of reductant concentration, light source, and light exposure duration were examined on X-Ag nanoparticle formation to achieve superior Raman EFs. Under optimal conditions (9.0 mM sodium citrate, 460 nm blue-LED at 10 W for 90 min), the combination of blue-LED-reduced Ag (B-Ag) and an Ag2FTO substrate (denoted as B-Ag-Ag2FTO) exhibited the best Raman EF of 2.79 × 105. This substrate enabled MG detection within a linear range of 0.1 to 1.0 µM (R2 = 0.98) and a detection limit of 0.02 µM. Additionally, the spiked recoveries in aquaculture water samples were between 90.0% and 110.0%, with relative standard deviations between 3.9% and 6.3%, indicating the substrate's potential for fungicide detection in aquaculture.

Green Synthesis of Carbon Quantum Dots and Carbon Quantum Dot-Gold Nanoparticles for Applications in Bacterial Imaging and Catalytic Reduction of Aromatic Nitro Compounds.

This study delves into the green synthesis and multifaceted applications of three types of carbon quantum dots (CQDs), namely, CQDs-1, CQDs-2, and CQDs-3. These CQDs were innovatively produced through a gentle pyrolysis process from distinct plant-based precursors: genipin with glucose for CQDs-1, genipin with extracted gardenia seeds for CQDs-2, and genipin with whole gardenia seeds for CQDs-3. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR), were employed to detail the CQDs' structural and surface characteristics, revealing their unique functional groups and surface chemistries. The study further explores the CQDs' bioimaging potential, where confocal fluorescence microscopy evidenced their swift uptake by Escherichia coli bacteria, indicating their suitability for bacterial imaging. These CQDs were also applied in the synthesis of gold nanoparticles (AuNPs), acting as reducing agents and stabilizers. Among these, CQD3-AuNPs were distinguished by their remarkable stability and catalytic efficiency, achieving a 99.7% reduction of 4-nitrophenol to 4-aminophenol in just 10 min and maintaining near-complete reduction efficiency (99.6%) after 60 days. This performance notably surpasses that of AuNPs synthesized using sodium citrate, underscoring the exceptional capabilities of CQD3-AuNPs. These insights pave the way for leveraging CQDs and CQD-stabilized AuNPs in bacterial imaging and catalysis, presenting valuable directions for future scientific inquiry and practical applications.

Nafion/Silver Nanoparticles as an Electrochemically Sensitive Interface for the Detection of Ractopamine in Pork Liver.

Many countries have allowed farmers to feed ß-adrenergic receptor agonists, such as ractopamine (Rac), to animals to improve the quality of their meat. However, Rac consumption can cause health problems for humans; thus, detecting Rac in meat before its packaging is essential. Consequently, this study developed a simple and sensitive electrochemical sensor by modifying a glassy carbon electrode (GCE) with Nafion/silver nanoparticles (Nafion/AgNPs). When this electrochemical sensor is used to detect Rac, electrostatic interaction occurs between Nafion and Rac, and the AgNPs oxidize Rac; thus, the accumulation and electrochemical sensing of Rac are achieved. Differential pulse voltammetry indicated that the as-prepared Nafion/AgNP-GCE sensor exhibited suitable electrochemical sensing ability under optimum conditions (6.0 µL of 0.10% Nafion/AgNPs in a Britton-Robertson buffer solution with a pH of 1.8, an accumulation potential of -0.2 V, and a Rac accumulation duration of 300 s). Moreover, this sensor has an extremely low limit of detection and high sensitivity (1.60 × 10-3 ppm and 2.14 µA/ppm, respectively) in the Rac concentration range 7.50 × 10-3-1.00 ppm. The as-prepared sensor also exhibits satisfactory reproducibility and storage stability, with the corresponding relative standard deviations (RSDs) being 4.27% (n = 5) and 1.56% (n = 10), respectively. The proposed electrochemical sensor was successfully used to determine the Rac content in pig liver samples, with spiked recoveries of 95.2-101.8% and RSDs of 0.55-4.83% being achieved.

Green synthesis of gardenia seeds-based carbon dots for bacterial imaging and antioxidant activity in aqueous and oil samples.

In this work, luminescent carbon dots with gardenia seeds as carbon precursors (GCDs) were synthesized using a one-step mild pyrolysis process and were then used as probes for imaging of bacterial (Escherichia coli). The GCDs showed a strong emission at 430 nm when excited at 370 nm. The relative fluorescence quantum yield of GCDs was found to be 1.13% in an aqueous medium. Rapid internalization of the GCDs by bacteria was confirmed by three colors (blue, green, and yellow) images that were obtained using confocal fluorescence microscopy. In addition, GCDs were noted to exhibit potent scavenging activities against DPPH˙, ˙OH, and ˙O2- free radicals. GCDs were also assayed as antioxidants in an oil sample by volumetric determination of the peroxide value. Thus, GCDs exhibited good antioxidant properties both in aqueous and oil media. In addition, a free fatty acid quantification kit in the presence of GCDs showed enhanced fluorescence detection of palmitic acid with a remarkably good limit of detection of 0.08 µM, which is lower than that in the absence of GCDs (0.76 µM). The proposed fluorescence method was then successfully used to determine the concentration of palmitic acid spiked in milk powder samples, with spiked recoveries of 82.6-109.6% and relative standard deviations of 0.9-4.6%.

Selective detection of tricyclazole by optical technique using thiomalic acid-modified Au and Ag nanoparticle mixtures.

This study proposes the use of thiomalic acid-modified Au and Ag nanoparticle mixtures (TMA-Au/AgNP mixes) for the selective detection of tricyclazole. Upon the addition of tricyclazole, the color of TMA-Au/AgNP mixes solution changes from orange-red to lavender (red-shift). According to the density-functional theory calculations, tricyclazole-induced aggregation of TMA-Au/AgNP mixes through electron donor-acceptor interactions was proved. The sensitivity and selectivity of the proposed method are affected by the amount of TMA, volume ratio of TMA-AuNPs to TMA-AgNPs, pH value, and buffer concentration. The ratio of absorbance (A654/A520) of TMA-Au/AgNP mixes solution is proportional to the concentration of tricyclazole over the range 0.1-0.5 ppm with a linear correlation (R2 = 0.948). Moreover, the limit of detection was estimated at 0.028 ppm. The practicality of TMA-Au/AgNP mixes was validated for the determination of tricyclazole concentration in real samples (spiked recovery was 97.5%-105.2%), demonstrating its advantages of simplicity, selectivity, and sensitivity.

Aminoglycoside-mimicking carbonized polymer dots for bacteremia treatment.

Bacteremia and associated bacterial sepsis are potentially fatal and occur when the host response to microbial invasion is impaired or compromised. This motivated us to develop carbonized polymer dots (CPDsMan/AA) from a mixture of mannose (Man) and positively charged amino acids [AAs; lysine, arginine (Arg), or histidine] through a one-step mild pyrolysis procedure, which effectively inhibited drug-resistant bacterial strains isolated from septic patients. The as-prepared CPDsMan/AA showed broad-spectrum antibacterial activity, including multidrug-resistant bacteria, even in human plasma. The minimal inhibitory concentration of CPDsMan/Arg is ca. 1.0 µg mL-1, which is comparable to or lower than those of other tested antibiotics (e.g., ampicillin, gentamicin, and vancomycin). In addition to directly disrupting bacterial membranes, the CPDsMan/Arg feature a structure similar to aminoglycoside antibiotics that could bind to 16S rRNA, thereby blocking bacterial protein synthesis. In vitro cytotoxic and hemolytic assays demonstrated the high biocompatibility of the CPDsMan/AA. In addition, in vivo studies on methicillin-resistant Staphylococcus aureus-infected mice treated with the CPDsMan/Arg showed a significant decrease in mortality-even better than that of antibiotics. Overall, the synthesis of the CPDsMan/AA is cost-efficient, straightforward, and effective for treating bacteremia. The polymeric features of the CPDsMan/Arg, including cationic charges and specific groups, can be recognized as a safe and broad-spectrum biocide to lessen our reliance on antibiotics to treat systemic bacterial infections in the future.

Au@Ag Dendritic Nanoforests for Surface-Enhanced Raman Scattering Sensing.

The effects of Au cores in Ag shells in enhancing surface-enhanced Raman scattering (SERS) were evaluated with samples of various Au/Ag ratios. High-density Ag shell/Au core dendritic nanoforests (Au@Ag-DNFs) on silicon (Au@Ag-DNFs/Si) were synthesized using the fluoride-assisted Galvanic replacement reaction method. The synthesized Au@Ag-DNFs/Si samples were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, reflection spectroscopy, X-ray diffraction, and Raman spectroscopy. The ultraviolet-visible extinction spectrum exhibited increased extinction induced by the addition of Ag when creating the metal DNFs layer. The pure Ag DNFs exhibited high optical extinction of visible light, but low SERS response compared with Au@Ag DNFs. The Au core (with high refractive index real part) in Au@Ag DNFs maintained a long-leaf structure that focused the illumination light, resulting in the apparent SERS enhancement of the Ag coverage.

Dendritic Forest-Like Ag Nanostructures Prepared Using Fluoride-Assisted Galvanic Replacement Reaction for SERS Applications.

Dendritic forest-like Ag nanostructures were deposited on a silicon wafer through fluoride-assisted galvanic replacement reaction (FAGRR) in aqueous AgNO3 and buffered oxide etchant. The prepared nanostructures were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-optical emission spectroscopy, a surface profiler (alpha step), and X-ray diffraction. Additionally, the dendritic forest-like Ag nanostructures were characterized using surface-enhanced Raman scattering (SERS) when a 4-mercaptobenzoic acid (4-MBA) monolayer was adsorbed on the Ag surface. The Ag nanostructures exhibited intense SERS signal from 4-MBA because of their rough surface, and this intense signal led to an intense local electromagnetic field upon electromagnetic excitation. The enhancement factor for 4-MBA molecules adsorbed on the Ag nanostructures was calculated to be 9.18 × 108. Furthermore, common Raman reporters such as rhodamine 6G, 4-aminothiolphenol, 5,5'-dithiobis-2-nitrobenzoic acid, and carboxyfluorescein (FAM) were characterized on these dendritic forest-like Ag nanostructures, leading to the development of an ultrasensitive SERS-based DNA sensor with a limit of detection of 33.5 nM of 15-mer oligonucleotide.

Silicon-Based Ag Dendritic Nanoforests for Light-Assisted Bacterial Inhibition.

Silver dendritic nanoforests (Ag-DNFs) on silicon (Ag-DNFs/Si) were synthesized through the fluoride-assisted Galvanic replacement reaction (FAGRR) method. The synthesized Ag-DNFs/Si were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), reflection absorbance spectrometry, surface-enhanced Raman scattering spectrometry, and X-ray diffractometry. The Ag+ concentration in ICP-MS measurements indicated 1.033 mg/cm2 of deposited Ag synthesized for 200 min on Si substrate. The optical absorbance spectra indicated the induced surface plasmon resonance of Ag DNFs increased with the thickness of the Ag DNFs layer. Surface-enhanced Raman scattering measurement and a light-to-heat energy conversion test presented the superior plasmonic response of Ag-DNFs/Si for advanced applications. The Ag-DNFs/Si substrate exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. The large surface area of the dense crystal Ag DNFs layer resulted in high antibacterial efficiency. The plasmonic response in the metal-crystal Ag DNFs under external light illumination can supply energy to enhance bacterial inhibition. High-efficiency plasmonic heating by the dense Ag DNFs can lead to localized bacterial inhibition. Thus, the Ag-DNFs/Si substrate has excellent potential for antibacterial applications.

Microwave-Assisted Synthesis of Chalcopyrite/Silver Phosphate Composites with Enhanced Degradation of Rhodamine B under Photo-Fenton Process.

A new composite by coupling chalcopyrite (CuFeS2) with silver phosphate (Ag3PO4) (CuFeS2/Ag3PO4) was proposed by using a cyclic microwave heating method. The prepared composites were characterized by scanning and transmission electron microscopy and X-ray diffraction, Fourier-transform infrared, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. Under optimum conditions and 2.5 W irradiation (wavelength length > 420 nm, power density = 0.38 Wcm-2), 96% of rhodamine B (RhB) was degraded by CuFeS2/Ag3PO4 within a 1 min photo-Fenton reaction, better than the performance of Ag3PO4 (25% degradation within 10 min), CuFeS2 (87.7% degradation within 1 min), and mechanically mixed CuFeS2/Ag3PO4 catalyst. RhB degradation mainly depended on the amount of hydroxyl radicals generated from the Fenton reaction. The degradation mechanism of CuFeS2/Ag3PO4 from the photo-Fenton reaction was deduced using a free radical trapping experiment, the chemical reaction of coumarin, and photocurrent and luminescence response. The incorporation of CuFeS2 in Ag3PO4 enhanced the charge separation of Ag3PO4 and reduced Ag3PO4 photocorrosion as the photogenerated electrons on Ag3PO4 were transferred to regenerate Cu2+/Fe3+ ions produced from the Fenton reaction to Cu+/Fe2+ ions, thus simultaneously maintaining the CuFeS2 intact. This demonstrates the synergistic effect on material stability. However, hydroxyl radicals were produced by both the photogenerated holes of Ag3PO4 and the Fenton reaction of CuFeS2 as another synergistic effect in catalysis. Notably, the degradation performance and the reusability of CuFeS2/Ag3PO4 were promoted. The practical applications of this new material were demonstrated from the effective performance of CuFeS2/Ag3PO4 composites in degrading various dyestuffs (90-98.9% degradation within 10 min) and dyes in environmental water samples (tap water, river water, pond water, seawater, treated wastewater) through enhanced the Fenton reaction under sunlight irradiation.

Detection of melamine based on the suppressed anodic response of uric acid by a Au-Ag nanoparticles modified glassy carbon electrode.

We demonstrated a sensitive electrochemical method for the determination of nonelectroactive melamine (Mel) using a modified glassy carbon electrode (GCE), with uric acid (UA) as the signal reporter. To increase the anodic response of UA, GCE was coated with Au-Ag nanoparticles and a Nafion thin film (Au-Ag/Nafion/GCE). The sensing mechanism was based on the competitive adsorption behavior of Mel on the Au-Ag/Nafion/GCE, which reduces the electroactive surface area of nanoparticles and thus hinders anodic response of UA. Under optimal conditions and the use of an analytical method of differential pulse voltammetry, this modified electrode detected Mel concentrations ranging from 2.5 to 70 nM, with a detection limit of 1.8 nM. The Au-Ag/Nafion/GCE demonstrated satisfactory reproducibility and stability, with relative standard deviations (RSDs) of 9.3% and 7.1%, respectively. The proposed electrochemical method was then successfully used to determine the Mel content in spiked milk powder and cat food samples, with RSDs of 1.7%-9.3% and recoveries of 92.4%-103.7%.

Carbon dots as artificial peroxidases for analytical applications.

Nanozymes have become attractive in analytical and biomedical fields, mainly because of their low cost, long shelf life, and less environmental sensitivity. Particularly, nanozymes formed from nanomaterials having high surface area and rich active sites are interesting since their activities can be tuned through carefully controlling their size, morphology, and surface properties. This review article focuses on preparation of carbon dots (C dots) possessing peroxidase-like activity and their analytical applications. We highlight the important roles of the oxidation states and surface residues of C dots and their nanocomposites with metal, metal oxides, or metal sulfides playing on determining their specificity and sensitivity toward H2O2. Examples of C dot nanozymes (CDzymes) for developing sensitive and selective absorption, fluorescence, and electrochemical sensing systems in the presence of substrates are presented to show their potential in analytical applications. For example, CDzymes couple with glucose oxidase and cholesterol oxidase are specific and sensitive for quantitation of glucose and cholesterol, separately, when using 3,3',5,5'-tetrame-thylbenzidine as the signal probe. This review article concludes with possible strategies for enhancing and tuning the catalytic activity of CDzymes.

Carbon quantum dots for the detection of antibiotics and pesticides.

Carbon quantum dots (CQDs) are novel nanomaterials with interesting physical and chemical properties, which are intensely studied only in the last decade. Unique properties, such as its inherent fluorescent property, high resistance to photobleaching, high surface area, ease of synthesis, flexible choice of precursor, and surface tunability enable CQDs for promising application in biosensing. Therefore, it is highly useful in clinical, forensic, medical, food and drug analyses, disease diagnosis, and various other fields of biosensing. In addition, their fluorescence properties are tunable by the interaction with certain molecules via different mechanisms, which enables their application for sensing of those molecules, such as pesticides and antibiotics. The detection of antibiotics and pesticides is especially important as they are commonly used in both the medical and agricultural fields and can affect both humans and their environment. However, these molecules do not have a specific recognition element unlike for antibodies, proteins, enzymes, and other biomarkers. Thus, the fluorescence quenching mechanism alone cannot be applied as a sensing mechanism for the CQDs-based sensing of pesticides and antibiotics. In this review, we discuss the application of various CQDs, in the detection of antibiotics, pesticides (herbicide, fungicide, insecticide), and other medicinal drugs through various detection strategies and their current limitations.

DNA engineered copper oxide-based nanocomposites with multiple enzyme-like activities for specific detection of mercury species in environmental and biological samples.

In this paper, we report the synthesis and application of enzyme-like DNA-copper oxide/platinum nanoparticles for the separate quantification of inorganic and organomercury species in various real samples. We synthesized a series of poly(thymine) (T60)-copper oxide/metal nanocomposites (T60-CuxO/M NCs; M = Au, Ag or Pt) that exhibited enzyme-like activities [oxidase (OX), peroxidase (POX), and catalase (CAT)]. The enzyme-like activities are tunable due to the incorporation of various metals into the NCs. Among a series of synthesized CuxO/M NCs, T60-copper oxide-platinum nanocomposites (T60-CuxO/Pt NCs) exhibited the highest OX-like activity via the O2-mediated oxidation of substrates, such as Amplex Red (AR), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), o-phenylenediamine (OPD), and 3,3',5,5'-tetramethylbenzidine (TMB), to form fluorescent or colored products. Interestingly, inorganic mercury ions (Hg2+) and organomercury species, such as methylmercury (MeHg+), ethylmercury (EtHg+), and phenylmercury (PhHg+), significantly inhibited the OX-like activity of T60-CuxO/Pt NCs. For the selective detection of mercury species, we used ABTS in the T60-CuxO/Pt NCs system, and the ABTS/T60-CuxO/Pt NCs-based assay allowed for the detection of mercury ions at nanomolar concentrations based on the decrease in the catalytic activity caused by the mercury ions. To separately quantify the inorganic and organomercury species in a sample, we employed selenium nanoparticles (Se NPs) as a masking agent, as they preferentially bind with inorganic mercury species. The ABTS/T60-CuxO/Pt NCs-based assay with the masking agent of Se NPs further provided specificity for the detection of organomercury species in environmental water samples (tap water, river water, and seawater) and fish muscle samples (dogfish muscle DORM-II).

Label-Free Colorimetric Detection of Mercury (II) Ions Based on Gold Nanocatalysis.

Herein, a label-free colorimetric nanosensor for Hg(II) is developed utilizing the hindering effect of Hg(II) on the kinetic aspect of gold nanoparticle (AuNPs) growth on the surface of gold nanostars (AuNSs). H-AuNS probes are synthesized and modified by 2-[4-(2-hydroxyethel) piperazine-1-yl] ethanesulfonic acid (HEPES). After the formulation of the reagents and testing conditions are optimized, HEPES-capped AuNSs (H-AuNSs) demonstrates good selectivity and sensitivity towards Hg(II) determination. A H-AuNS probe, in the presence of HCl/Au(III)/H2O2, is capable of detecting a Hg(II) concentration range of 1.0 nM⁻100 µM, with a detection limit of 0.7 nM, at a signal-to-noise ratio of 3.0, and a visual detection limit of 10 nM with naked eyes. For practicality, the H-AuNS probe is evaluated by measuring Hg(II) in the environmental water matrices (lake water and seawater) by a standard addition and recovery study. The detection limits for environmental samples are found to be higher than the lab samples, but they are still within the maximum allowable Hg concentration in drinking water (10 nM) set by the US Environmental Protection Agency (EPA). To create a unique nanosensor, the competitive interaction between Hg(II) and Pt(IV) toward the H-AuNSs probe is developed into a logic gate, improving the specificity in the detection of Hg(II) ions in water samples.

Facile Synthesis and Characterization of Ag3PO4 Microparticles for Degradation of Organic Dyestuffs under White-Light Light-Emitting-Diode Irradiation.

This study demonstrated facile synthesis of silver phosphate (Ag3PO4) photocatalysts for the degradation of organic contaminants. Ag3PO4 microparticles from different concentrations of precursor, AgNO3, were produced and characterized by scanning electron microscopy, powder X-ray diffraction, and UV⁻visible diffuse reflectance spectroscopy. Degradation rates of methylene blue (MB) and phenol were measured in the presence of microparticles under low-power white-light light-emitting-diode (LED) irradiation and the reaction rate followed pseudo-first-order kinetics. The prepared Ag3PO4 microparticles displayed considerably high photocatalytic activity (>99.8% degradation within 10 min). This can be attributed to the microparticles' large surface area, the low recombination rate of electron⁻hole pairs and the higher charge separation efficiency. The practicality of the Ag3PO4 microparticles was validated by the degradation of MB, methyl red, acid blue 1 and rhodamine B under sunlight in environmental water samples, demonstrating the benefit of the high photocatalytic activity from Ag3PO4 microparticles.

Determination of mercury (II) ions based on silver-nanoparticles-assisted growth of gold nanostructures: UV-Vis and surface enhanced Raman scattering approaches.

Innovative dual detection methods for mercury(II) ions (Hg(II)) have been developed based on the formation of gold nanostructures (AuNSs) following the addition of mercury-containing solution to a mixture containing an optimized amount of Au(III), H2O2, HCl, and silver nanoparticles (AgNPs). In the absence of Hg(II), the addition of Au(III), H2O2, and HCl to the AgNP solution changes the solution's color from yellow to red, and the absorption peak shifts from 400 to 526nm, indicating the dissolution of AgNPs and the formation of gold nanoparticles (AuNPs). Because of the spontaneous redox reaction of Hg(II) toward AgNPs, the change in the amount of remaining AgNP seed facilitates the generation of irregular AuNSs, resulting in changes in absorption intensity and shifting the peak within the range from 526 to 562nm depending on the concentration of Hg(II). Under optimal conditions, the limit of detection (LOD) for Hg(II) at a signal-to-noise ratio (S/N) of 3 was 0.3µM. We further observed that AgNP-assisted catalytic formation of Au nanomaterials deposited on a surface enhanced Raman scattering active substrate significantly reduced the Raman signal of 4-mercaptobenzoic acid, dependent on the Hg(II) concentration. A linear relationship was observed in the range 0.1nM-100µM with a LOD of 0.05nM (S/N 3.0). As a simple, accurate and precise method, this SERS-based assay has demonstrated its success in determining levels of Hg(II) in real water samples.

Determination of salicylic acid using a magnetic iron oxide nanoparticle-based solid-phase extraction procedure followed by an online concentration technique through micellar electrokinetic capillary chromatography.

In this study, a magnetic iron oxide nanoparticle-based solid-phase extraction procedure combined with the online concentration and separation of salicylic acid (SA) through micellar electrokinetic chromatography-UV detection (MEKC-UV) was developed. Under optimal experimental conditions, a good linearity in the range of 0.01-100µmolL-1 was obtained with a coefficient of correlation of 0.9999. The detection sensitivity of the proposed method exhibited an approximately 1026-fold improvement compared with a single MEKC method without online concentration, and the detection limit (S/N=3) was 3.80nmolL-1. The repeatability of the method was evaluated using intraday and interday RSDs (11.5% and 17.0%, respectively). The method was used to determine SA concentrations in tobacco leaves (Nicotiana tabacum L. cv. Samsun) from the NN genotype, nn genotype, and Nt-NahG mutant strains, as well as in shampoo and ointment samples. Rapid extraction and separation (<50min), acceptable repeatability (RSD<17.0%), and high spiked recoveries (95.8%-102.4%) were observed for plants, detergents, and pharmaceuticals.